Radiation-curable inkjet inks contain radiation-curable material, such as radiation-curable monomers, which polymerise by irradiation with actinic radiation (usually ultraviolet light) in the presence of a photoinitiator. In inkjet printing, the inks must flow rapidly through the printing heads and hence they must have a low viscosity when jetted. The inks must also be resistant to drying or crusting in the reservoirs or nozzles. This places particular demands on the ink formulator, who also has to balance the requirements of the particular technical application, including adhesion to the substrate, flexibility, durability and the aesthetic quality of the final image.
Tetrahydrofurfuryl acrylate (THFA) is often used to provide good adhesion to variety of substrates, as well as producing a flexible film which is less liable to cracking and delamination. A further advantage of THFA is that it can solubilise chlorinated polyolefins, which in turn provides good adhesion to polyolefin substrates.
However, THFA is a hazardous monomer and bears the GHS hazard statement H314 (Causes severe skin burns and eye damage). There is also growing evidence that it may damage fertility or the unborn child. Thus, there is an urgent need in the art to move away from THFA.